FRQ — Thermodynamics

Long answer·Hard exam skill (4/5)·No calculator

Difficulty guide

The label describes the problem, not your ability.

1/5 - Foundational

Warm-up setup; checks one basic idea.

2/5 - Routine exam skill

Normal syllabus skill; usually one main rule or interpretation.

3/5 - Standard multi-step

Exam-style problem with multiple steps or a common trap.

4/5 - Hard exam skill

High-end exam problem; combines methods carefully.

5/5 - Challenge

Stretch problem beyond normal exam pressure.

Question

A gas passes through a complete cycle

A\to B\to C\to A

. In

A\to B

, it absorbs

500\text{ J}

of heat and does

200\text{ J}

of work. In

B\to C

, it rejects

100\text{ J}

of heat and

150\text{ J}

of work is done on it. In

C\to A

, it rejects

250\text{ J}

of heat.

Total: 4 marks

(a) Find $\Delta U$ for $A\to B$ . (1 mark)

(b) Find $\Delta U$ for $B\to C$ . (1 mark)

(d) Find the work done by the gas in $C\to A$ . (1 mark)

Your response (optional — you can also work on paper)

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